1. Technical Field
The present invention in embodiments relates generally to data compression and decompression and, more particularly, to devices and method for the compression of printing hints by processing saturated pixels with different rendering hint values in a very similar manner; for example, similar enough to be indistinguishable by the eye.
2. References
Digital color imaging on high-resolution printers such as xerographic printers requires the handling of large amounts of video data for each page. The color image for each page is typically represented as a set of four color planes, usually cyan, magenta, yellow, and black. Each color plane is a set of scanlines and each scanline is a sequence of individual image pixels.
The image quality can be improved using object optimized printing as described by Motamed in U.S. Pat. No. 5,687,303. With object optimized printing, printing hints in the form of metabits are generated for each image pixel and sent to an IOT (Image Output Terminal). The printing hints, which are utilized by a CRM (Contone Rendering Module) within the printer, can optimize such processing subsystems as halftone generation, halftone screen size and angle, color space transformation, tone reproduction curve, IOT output correction, and the like.
The printing hints may improve the quality of the printed output; however, they also may increase that amount of data required to represent the color images. It is often desirable to reduce the size of the color images and printing hints to reduce the amount of solid state memory required to buffer the images, reduce the amount of disk space to store the images, and speed up transfer of the images within the printing system. This may be accomplished by compressing the page images and printing hints after they are generated and decompressing them immediately before they are needed for printing.
There are a number of different compression schemes to reduce the size of the page images. One such method is to use the lossy or lossless JPEG compression standard. Better compression can be achieved with more complex algorithms. The printing hints should be compressed using a lossless algorithm such as run length coding or a lossless adaptive dictionary-based coding such as described by Eastman in U.S. Pat. No. 4,464,650.
The compressed size of the printing hints is dependent on the lossless compression algorithm used and the complexity of the printing hints. The compressed size of the printing hints can be reduced by reducing the complexity of the printing hints.